Welcome to http://hou.lbl.gov/~vhoette/OpenStarClusters

Open Star Clusters

Open, or galactic, star clusters are found in the spiral arms of the Milky Way.  They usually have younger stars which are often more blue in color.  

  
Many open clusters are difficult to image on a small CCD chip which is mounted on a big telescope.  They are usually larger than the field of view.  It is best to look at open clusters with binoculars or to image them with small telescopes or camera lenses which have a wide field of view. 

Most of the stars in NGC 884, the open cluster in Perseus, are blue.
Can you find two red stars?

Adler Planetarium's  HOU teachers took images in red, green and blue filters using the TIE Mt. Wilson 24 inch telescope with an SBIG ST-6 CCD.   Compare the colors of the cluster stars by using Auto aperture or Find to record and compare brightness counts.  Most of the stars are more bluish.  However, there are two distinctly red stars.  Find these two very red stars! 
Make a chart to record the position of each star on the images and the brightness counts in red, green and blue.  Tally by color as many stars as you can analyze.  Describe the distribution of stars by color in the open cluster, NGC 884. 

Note: Image exposure times are in a ratio of red:1, green:2, blue:3 as recommended by the telescope operator to adjust for the red sensitivity of the SBIG ST-6 CCD chip.   The green image was further altered to create a more accurate color balance among the images. 

HOU Educators: Download .fts images.
Yerkes 2 inch refractor, image of double cluster in Perseus:  n884_869.fts
Oil City Astronomical Society's Pleiades image:  m45_ocas.fts
Yerkes 2 inch refractor, Pleiades image: pleiades.fts
TIE Mt. Wilson 24inch Reflector's red, green, and blue images:  NGC884

11/24/99

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